Maybe it is because I first learned kernel coding with Linux but I find that to be the exact opposite. I had a much harder time figuring out BSD and OpenSolaris kernel code for my NFS work than I did with the Linux NFS implementation. In terms of coding style I often run into projects that I wish had the same coding style as the kernel. The code is formatted in a way that is easy to read. The size of functions are mostly pretty easy to handle. The organization of the code in the tree's hierarchy makes sense. The layering in the kernel is handled pretty well. It may just be a case of familiarity since I've been working on Linux for so long but I had a hard time with other unix operating systems.